Cavitating jet device

Abstract

A device for applying cavitating liquid jets to a work surface has an annular work surface engaging area surrounding a chamber, recessed into the device and with an open end adjacent the working surface, a jet nozzle on the opposite side of the chamber which projects a high velocity liquid jet against the working surface, and passages extending from the chamber to the interior of the tool and providing the main route for escape of spent liquid, the passages being calibrated so as to maintain the chamber full of liquid without engendering a substantial pressure rise within the chamber. The velocity of the liquid jet is high enough that shear between the jet and the spent liquid causes cavitation.

I claim: 
     
       1. A liquid jet device for direct application to a working surface to be treated, comprising a body defining walls of a cavitation chamber, the chamber having an open end facing the working surface and the body being shaped to contact the working surface in a continuous annular zone surrounding the open side of the cavitation chamber, a source of high pressure liquid, a jet nozzle connected to said source and supported in said body on a side of the cavitation chamber opposite said open end and directed towards said open end so that a jet of high pressure liquid ejected from said nozzle will impact the working surface in a zone within and spaced from said annular zone, at least one vent opening in the walls of the cavitation chamber and spaced from said open end, the flow capacity of said at least one vent opening being large compared with leakage between the annular zone and the working surface, large enough to exhaust the liquid from said cavitation chamber without engendering a pressure rise in the chamber sufficient to suppress cavitation therein, and small enough to ensure retention of sufficient liquid in the chamber to submerge the liquid jet, the working pressure of the source of high pressure liquid, the dimensions of the jet nozzle and the distance between the nozzle and the open end of the cavitation chamber being such that shear between the liquid jet and the liquid retained in the chamber will induce cavitation vortices and sustain them until impact with the working surface. 
     
     
       2. A device according to claim 1, wherein the body is a distal portion of a rod, the chamber is a cylindrical bore extending coaxially into the rod from its distal end, the nozzle is located at the inner end of the chamber coaxial with the rod, and the vent openings are formed by bores extending between the longitudinal surface of the rod and the cylindrical bore. 
     
     
       3. Apparatus according to claim 1, wherein the working pressure of the liquid source is about 200 to about 800 atmospheres. 
     
     
       4. A method for cutting, eroding or fragmenting a solid material, comprising placing in intimate contact with a working surface of the material to be treated a body defining walls of a cavitation chamber, the chamber having an open end facing the working surface and the body being shaped to bed against the working surface in a continuous annular zone surrounding the open side of the cavitation chamber, supplying high pressure liquid to a jet nozzle supported in said body on a side of the cavitation chamber opposite said open end and directed towards said open end so that a jet of high pressure liquid ejected from said nozzle impacts the working surface in a zone within and spaced from said annular zone, venting liquid from said chamber through at least one vent opening in the walls of the cavitation chamber and spaced from said open end, the flow through said at least one vent opening being large compared with leakage between the annular zone and the working surface, large enough to exhaust the liquid from said cavitation chamber without engendering a pressure rise in the chamber sufficient to suppress cavitation therein, and small enough to ensure retention of sufficient liquid in the chamber to submerge the liquid jet, the pressure of high pressure liquid being maintained at a sufficient level, relative to the dimensions of the jet nozzle and the distance between the nozzle and the open end of the cavitation chamber, that shear between the liquid jet and the liquid retained in the chamber induces cavitation vortices and sustains them until impact with the working surface. 
     
     
       5. A method according to claim 4, wherein the pressure of the high pressure liquid is between 200 and 800 atmospheres.